1. Field of the Invention
The present invention relates to an electrode for a lithium ion secondary battery and a lithium ion secondary battery.
2. Related Background Art
As a safety measure for a lithium ion secondary battery, a method of forming a protecting layer on the surface of an electrode (negative electrode) has been proposed (see, for example, Japanese Patent Laid-Open No. 7-220759, International Publication No. WO 97/01870 and Japanese Patent Laid-Open No. 11-54147).
The protecting layer is basically formed by depositing a particle. The particle size and particle size distribution, in this case, have an effect upon the characteristics of the battery such as rate characteristics and charge-discharge cycle characteristics, and safety such as internal short circuit caused by dendrite formation. In a conventional protecting layer, an inorganic particle is basically used. When an inorganic particle is used, it is difficult to control the particle size and particle size distribution. Therefore, a small-size inorganic particle is selected to form a protecting layer having a uniform thickness.
The conventional protecting layer is basically formed by depositing an inorganic particle.
The conventional protecting layer is basically formed by depositing an inorganic particle. However, an inorganic particle has a wide particle size distribution. To form a protecting layer having uniform thickness, a small-size inorganic particle is selected.
As a lithium ion secondary battery, one having a pair of electrodes facing each other and a separator interposed between the electrodes is known. In a process for manufacturing such a lithium ion secondary battery, when the separator is broken by e.g., convexoconcave of an electrode surface, short circuit occurs between the electrodes facing each other, generating heat. To prevent occurrence of such a problem, a technique of forming a protecting layer using an inorganic particle and an organic particle on a surface of an active-material containing layer has been proposed (see, for example, Japanese Patent Laid-Open No. 7-220759, International Publication No. WO97/01870 and Japanese Patent Laid-Open No. 11-54147).